As one of the most endangered primate species in the world, sightings of the elusive Tonkin snub-nosed monkey are rare. Its no wonder a recent sighting of a group in Vietnam has proved cause for celebration.

A pioneering study to gauge the toxicity of quantum dots in primates has found the tiny crystals to be safe over a one-year period, a hopeful outcome for doctors and scientists seeking new ways to battle diseases like cancer ...

Dan the baboon sits in front of a computer screen. The letters BRRU pop up. With a quick and almost dismissive tap, the monkey signals it's not a word. Correct. Next comes, ITCS. Again, not a word. Finally KITE comes up.

Monkey

Cebidae
Aotidae
Pitheciidae
Atelidae
Cercopithecidae

A monkey is any cercopithecoid (Old World monkey) or platyrrhine (New World monkey) primate. All primates that are not prosimians (lemurs and tarsiers) or apes are monkeys. The 264 known extant monkey species represent two of the three groupings of simian primates (the third group being the 21 species of apes). Monkeys are usually smaller and/or longer-tailed than apes.

The New World monkeys are classified within the parvorder Platyrrhini, whereas the Old World monkeys (superfamily Cercopithecoidea) form part of the parvorder Catarrhini, which also includes the apes. Thus, scientifically speaking, monkeys are paraphyletic (not a single coherent group), and Old World monkeys are actually more closely related to the apes than they are to the New World monkeys.

Due to its size (up to 1 m/3 ft) the Mandrill is often thought to be an ape, but it is actually an Old World monkey. Also, a few monkey species have the word "ape" in their common name.